The present invention relates to an article positioning mechanism, and in particular relates to such a mechanism in which an article consisting of a component or a tool is held by a holder member that has a tapered male engagement portion, a frame shaped member that has a tapered female engagement portion is provided on a mounting portion of a movable member of a mechanical device, and positioning and rotational restriction are performed by the tapered male engagement portion being engaged with the tapered female engagement portion in a closely contacting manner.
In the past, when processing a workpiece with a mechanical device of some type such as a machine tool or a robot or the like, an article associated with this task such as a component or a tool or the like must be positioned via a holder member with respect to a mounting portion of a movable member of the mechanical device, along with its rotation being restricted. In order to do this, article positioning mechanisms of various types have been developed and implemented in practice that are capable of positioning an article at good accuracy while also reliably restricting its rotation. In particular, in order to process a workpiece at high accuracy with a machine tool, it is necessary to position a tool holder that is holding a rotational tool or a machining tool or the like at high accuracy with respect to the main axis of the machine tool or with respect to a turret thereof, while also reliably restricting its rotation.
Now, as such an article positioning mechanism described above, for example, in Patent Document #1 there is disclosed a positioning mechanism for positioning a tool holder on a turret of a tool post at high accuracy. With this positioning mechanism, four concave shaped key grooves are formed on an outer peripheral neighboring portion of a turret mounting surface of the tool holder, and three convex shaped keys are formed on a holder mounting surface of the turret of the tool post so as to correspond to these key grooves. When the tool holder is attached to the turret, by the mounting surface of the tool holder being contacted against the mounting surface of the turret and each one of three of the four key grooves being engaged with the one of the three keys that corresponds thereto, the tool holder is positioned in the vertical direction and also in the horizontal direction with respect to the mounting surface of the turret, and moreover its rotation with respect to the turret is restrained.    Patent Document #1: Japanese Laid Open Patent Publication 2006-167862.
However, with the positioning mechanism of Patent Document #1 described above, in order for the engagement surfaces of the plurality of key grooves to engage reliably with the engagement surfaces of the plurality of keys, it is necessary to perform minute adjustment of the sizes of the various keys and of the various key grooves that correspond to them. In order to make these minute adjustments, as a final process, it is necessary to perform comparison and adjustment by hand, and this task consumes a great deal of labor and time. Since a slight clearance needs to be present between the engagement surfaces of each of the keys and each of the key grooves in order for each of the plurality of keys to engage with each of the plurality of key grooves, it becomes very difficult to improve the positioning accuracy as far as, for example, 2 or 3 μm.
Moreover since the task of engaging each of the plurality of key grooves with its corresponding key takes a great deal of labor, accordingly there is a fear that, while contacting the turret fitting surface of the tool holder against the holder fitting surface of the turret, damage will be caused to the engagement surfaces of the key grooves and to the engagement surfaces of the keys, and this would decrease the durability. Furthermore there is also the problem that, when positioning the plurality of keys with the plurality of key grooves, the force for restricting mutual rotation may become weak due to inadequacy of rigidity of the keys or of the key grooves, since these structural members are small in size,
The objects of the present invention are to provide an article positioning mechanism that is capable of reliably restricting rotation while also being capable of positioning at high accuracy, to provide an article positioning mechanism whose strength and durability are excellent, and so on.
The article positioning mechanism of the present invention is an article positioning mechanism for positioning of an article comprising a component or a tool with respect to a mounting portion of a movable member of a mechanical device so as to restrict the rotation thereof, characterized by comprising a holder member to which the article is fixed and a frame shaped member fixed to the mounting portion, the holder member comprising a position regulation surface that is orthogonal to an axis of the mounting portion, and a tapered male engagement portion formed in a regular polygonal shape that, in cross section in the direction orthogonal to the axis, has a plurality of circular arcuate corner portions that are convex outwards and a plurality of side portions, and that is sloped in such a manner that the closer the tapered male engaging portion is to the mounting portion, the closer the tapered male engaging portion is to the axis, the frame shaped member comprising a reference surface that receives and stops the position regulation surface and positions it in the axial direction, and a tapered female engagement portion formed in a regular polygonal shape that, in cross section in the direction orthogonal to the axis, has a plurality of circular arcuate corner portions that are convex outwards and a plurality of side portions, and that moreover slopes in the same direction as the tapered male engagement portion; and, when the holder member is fixed to the mounting portion or to the frame shaped member by a fixing means, the tapered male engagement portion is engaged to the tapered female engagement portion in a closely contacting manner via elastic deformation of the outer peripheral side wall portion of the tapered female engagement portion in the radial direction outwards from the axis and in the direction to approach the mounting portion